Heretofore, there have been known 8-amino-4,4a,5,6-tetrahydro-2H-benzo[h]cinnolin-3-one possessing platelet aggregation-suppressing actions, vasodilating actions, antiulcer actions and so on in Japanese Patent Application Laid-open (Kokai) No. 47468/1986; benzo[h]cinnoline derivatives possessing anxiolytic actions, platelet aggregationsuppressing actions, diuretic actions and antidotal actions against administration of an excessive amount of anxiolytics in Kokai No. 56169/1986; benzothiopyrano[4,3-c]pyridazine compounds possessing anxiolytic actions or antidotal actions against administration of an excessive amount of anxiolytics in W087/04162 and (1)benzopyrano[4,3-c]pyridazin-3-one compounds in Bulletin of the Chemical Society of Japan, vol. 55, pp. 2450-2455 (1982) respectively as fused pyridazine compounds exhibiting pharmacological activities.
Meanwhile, there is a growing trend toward increase of human diseases which are caused by disorders in immune function such as autoimmunity diseases, infectious diseases, immuno-deficiency diseases and so on.
It is known that an adrenal cortical hormone which is one of the widely-used therapeutic medicines for the immune disorder diseases exhibits a drastic effect thereon, while it brings about serious side effects such as immune function deficiency, infectious diseases and edema.
The object of this invention resides in providing compounds with low level of side effects, which are useful for the prophylaxis and therapy of various diseases associated with immune function deficiency.